It is our overall goal to examine the mechanisms by which HIV infects cells of the lymphoid system, and to study the consequences of this infection for both T and non-T cells. We have three major aims. First, we will examine the T cell-mediated immune response to the HIV envelope glycoprotein, gp120. These experiments are initiated by the preliminary observations of Lee et al. on the humoral responses to the intact or non-reduced (NR) gp120 glycoprotein and a reduced (R) form of the gp120 glycoprotein. Briefly, preliminary studies suggest a correlation between the ratio of response to reduced and non-reduced forms of the gp120 glycoprotein and eventual outcome of HIV infection. We will examine and quantify the antigen specific T cell proliferative and cytotoxic response in patients at different stages of infection to the R and NR forms of the gp120 peptide. Using synthetic peptides of gp120 we will identify and map the precise site on the gp120 glycoprotein which is immunogenic. T cell proliferation to the peptides as well as antigen-induced secretion of interferon gamma, interleukin-4 (BSF-1/IL-4) and interleukin-2 (IL-2) will be measured. T cell surface phenotype (T4, T8, T3, IL-2 receptor, Ia) before and after activation by the gp120 peptides will also be determined. We will determine whether synthetic peptides of gp120 can block the binding of HIV to T4 inhibit syncytia formation. Second, the role of T4 in infectivity by HIV will be examined by the production of murine-human recombinant T4 genes and human T4 genes with site-directed mutations, and transfection of such genes into human T4-negative cells. The relative infectibility of such transfected cells and their ability to form syncytia will then be determined. We will also examine the relationship of T4 molecules to HIV proteins in intracytoplasmic compartments by immunoelectromicroscopy. Since the T4 molecule associates with class II major histocompatibility complex (MHC) molecules on antigen-presenting cells (APC) during the initiation of an immune response, the role of class II molecules in controlling HIV-III infection will be examined by determining the relative infectibility of T4+ T cells in the presence and absence of Class II positive APC and in the presence and absence of blocking antibodies to class II. Third, we will determine the effect of the trans-activator proteins from HTLV-I-II, and HIV on the expression of lymphoid- specific cellular genes by transfection of these cDNAs into murine and human T cells, B cells and macrophages. Preliminary data suggest that both tat 1 and tat 2 induce the expression of class II MHC molecules and IL-2 receptor genes in cells of the B lineage.